JP8-40136A discloses a mixer drum apparatus mounted on a concrete mixer truck. This mixer drum apparatus includes a rotating drum, a hopper that directs charged ready-mixed concrete to the drum, an inlet seal that is provided at an opening end of the drum and is connected to the hopper, and a pair of blades that spirally extend from the opening end of the drum to the front side of the concrete mixer truck (back side of the drum).
The inlet seal has an inlet seal pipe that is connected to an outlet of the hopper, and a pair of inlet seal panels that extend from the inlet seal pipe to the back side of the drum to be connected to inner peripheries of the blades.
When charging the ready-mixed concrete, the inlet seal pipe directs the ready-mixed concrete that is charged to the hopper to the back side of the drum.
At the time of stirring or mixing with the ready-mixed concrete being loaded closer to a maximum load, the inlet seal panels receive the ready-mixed concrete that is over the inner peripheries of the blades in the vicinity of the opening end of the drum, thereby preventing the ready-mixed concrete from being discharged from the opening end of the drum.